Selective cobalt deposition on copper surfaces

ABSTRACT

Embodiments of the invention provide processes to selectively form a cobalt layer on a copper surface over exposed dielectric surfaces. In one embodiment, a method for capping a copper surface on a substrate is provided which includes positioning a substrate within a processing chamber, wherein the substrate contains a contaminated copper surface and a dielectric surface, exposing the contaminated copper surface to a reducing agent while forming a copper surface during a pre-treatment process, exposing the substrate to a cobalt precursor gas to selectively form a cobalt capping layer over the copper surface while leaving exposed the dielectric surface during a vapor deposition process, and depositing a dielectric barrier layer over the cobalt capping layer and the dielectric surface. In another embodiment, a deposition-treatment cycle includes performing the vapor deposition process and subsequently a post-treatment process, which deposition-treatment cycle may be repeated to form multiple cobalt capping layers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to a metallization processfor manufacturing semiconductor devices, more particularly, embodimentsrelate to preventing copper dewetting by depositing cobalt materials ona substrate.

2. Description of the Related Art

Copper is the current metal of choice for use in multilevelmetallization processes that are crucial to semiconductor devicemanufacturing. The multilevel interconnects that drive the manufacturingprocesses require planarization of high aspect ratio apertures includingcontacts, vias, lines, and other features. Filling the features withoutcreating voids or deforming the feature geometry is more difficult whenthe features have higher aspect ratios. Reliable formation ofinterconnects is also more difficult as manufacturers strive to increasecircuit density and quality.

As the use of copper has permeated the marketplace because of itsrelative low cost and processing properties, semiconductor manufacturerscontinue to look for ways to improve the boundary regions between copperand dielectric material by reducing copper diffusion and dewetting.Several processing methods have been developed to manufacture copperinterconnects as feature sizes have decreased. Each processing methodmay increase the likelihood of errors such as copper diffusion acrossboundary regions, copper crystalline structure deformation, anddewetting. Physical vapor deposition (PVD), chemical vapor deposition(CVD), atomic layer deposition (ALD), chemical mechanical polishing(CMP), electrochemical plating (ECP), electrochemical mechanicalpolishing (ECMP), and other methods of depositing and removing copperlayers utilize mechanical, electrical, or chemical methods to manipulatethe copper that forms the interconnects. Barrier and capping layers maybe deposited to contain the copper.

In the past, a layer of tantalum, tantalum nitride, or copper alloy withtin, aluminum, or magnesium was used to provide a barrier layer or anadhesion promoter between copper and other materials. These options arecostly or only partially effective or both. As the copper atoms alongthe boundary regions experience changes in temperature, pressure,atmospheric conditions, or other process variables common duringmultiple step semiconductor processing, the copper may migrate along theboundary regions and become agglomerated copper. The copper may also beless uniformly dispersed along the boundary regions and become dewettedcopper. These changes in the boundary region include stress migrationand electromigration of the copper atoms. The stress migration andelectromigration of copper across the dielectric layers or otherstructures increases the resistivity of the resulting structures andreduces the reliability of the resulting devices.

Barrier layers containing cobalt have been deposited by PVD, CVD, andALD processes. PVD processes to deposit cobalt are often hard to controlprecise deposition thicknesses. CVD processes usually suffer from poorconformality and contaminants in the deposited cobalt layer. During atypical ALD process, a cobalt precursor and a reducing agent aresequentially exposed to a substrate to form the desired cobalt layer.ALD processes have several advantages over other vapor depositionprocesses, such as very conformal films and the ability to deposit intohigh aspect ratio vias. However, the deposition rates of an ALD processare often too slow, so that ALD processes are not often used incommercial applications.

Therefore, a need exists to enhance the stability and adhesion ofcopper-containing layers, especially for copper seed layers. Also, aneed exists to improve the electromigration (EM) reliability ofcopper-containing layer, especially for copper line formations, whilepreventing the diffusion of copper into neighboring materials, such asdielectric materials. A further need exists for an improved vapordeposition process to deposit cobalt materials.

SUMMARY OF THE INVENTION

Embodiments of the invention provide processes to selectively form acobalt layer on a copper surface over exposed dielectric surfaces. Inone embodiment, a method for capping a copper surface on a substrate isprovided which includes positioning a substrate within a processingchamber, wherein the substrate contains a contaminated copper surfaceand a dielectric surface, exposing the contaminated copper surface to areducing agent while forming a metallic copper surface during apre-treatment process, exposing the substrate to a cobalt precursor gasto selectively form a cobalt capping layer over the metallic coppersurface while leaving exposed the dielectric surface during a vapordeposition process, and depositing a dielectric barrier layer over thecobalt capping layer and the dielectric surface.

In some examples, the method further includes chemically reducing copperoxides on the contaminated copper surface to form the metallic coppersurface during the pre-treatment process. The contaminated coppersurface may be exposed to the reducing agent and a plasma is ignitedduring the pre-treatment process, the reducing agent may contain areagent such as nitrogen (N₂), ammonia (NH₃), hydrogen (H₂), anammonia/nitrogen mixture, or combinations thereof. In some examples, thecontaminated copper surface may be exposed to the plasma for a timeperiod within a range from about 5 seconds to about 15 seconds. Inanother example, the reducing agent contains hydrogen gas, thepre-treatment process is a thermal process, and the substrate is heatedto a temperature within a range from about 200° C. to about 400° C.during the thermal process.

In other examples, the method further includes exposing the cobaltcapping layer to a reagent and a plasma during a post-treatment processprior to depositing the dielectric barrier layer. The reagent maycontain nitrogen, ammonia, hydrogen, an ammonia/nitrogen mixture, orcombinations thereof.

In another embodiment, a deposition-treatment cycle includes performingthe vapor deposition process and subsequently the post-treatmentprocess, and the deposition-treatment cycle is performed 2, 3, or moretimes to deposit multiple cobalt capping layers. Each of the cobaltcapping layers may be deposited to a thickness within a range from about3 Å to about 5 Å during each of the deposition-treatment cycles. Theoverall cobalt capping material or cobalt capping layer may have athickness within a range from about 4 Å to about 20 Å. In some examples,the cobalt capping layer has a thickness of less than about 10 Å.

The substrate may be exposed to a deposition gas containing the cobaltprecursor gas and hydrogen gas during the vapor deposition process, thevapor deposition process is a thermal chemical vapor deposition processor an atomic layer deposition process. wherein the cobalt precursor gascontains a cobalt precursor which has the general chemical formula(CO)_(x)Co_(y)L_(z), wherein X is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or12; Y is 1, 2, 3, 4, or 5; Z is 1, 2, 3, 4, 5, 6, 7, or 8; and L is aligand independently selected from cyclopentadienyl,alkylcyclopentadienyl, methylcyclopentadienyl,pentamethylcyclopentadienyl, pentadienyl, alkylpentadienyl,cyclobutadienyl, butadienyl, allyl, ethylene, propylene, alkenes,dialkenes, alkynes, nitrosyl, ammonia, derivatives thereof, orcombinations thereof. The cobalt precursor gas may contain a cobaltprecursor selected from the group consisting of tricarbonyl allylcobalt, cyclopentadienyl cobalt bis(carbonyl), methylcyclopentadienylcobalt bis(carbonyl), ethylcyclopentadienyl cobalt bis(carbonyl),pentamethylcyclopentadienyl cobalt bis(carbonyl), dicobaltocta(carbonyl), nitrosyl cobalt tris(carbonyl), bis(cyclopentadienyl)cobalt, (cyclopentadienyl) cobalt (cyclohexadienyl), cyclopentadienylcobalt (1,3-hexadienyl), (cyclobutadienyl) cobalt (cyclopentadienyl),bis(methylcyclopentadienyl) cobalt, (cyclopentadienyl) cobalt(5-methylcyclopentadienyl), bis(ethylene) cobalt(pentamethylcyclopentadienyl), derivatives thereof, complexes thereof,plasmas thereof, or combinations thereof. In one example, the cobaltprecursor contains cyclopentadienyl cobalt bis(carbonyl).

In another embodiment, a method for capping a copper surface on asubstrate is provided which includes positioning a substrate within aprocessing chamber, wherein the substrate contains a copper oxidesurface and a dielectric surface, exposing the copper oxide surface toan ammonia plasma or a hydrogen plasma while forming a metallic coppersurface during a pre-treatment process, exposing the substrate to acobalt precursor gas to selectively form a cobalt capping layer over themetallic copper surface while leaving exposed the dielectric surfaceduring a vapor deposition process, exposing the cobalt capping layer toa plasma during a post-treatment process, and depositing a dielectricbarrier layer over the cobalt capping layer and the dielectric surface.

In some examples, a deposition-treatment cycle is formed by performingthe vapor deposition process and subsequently the post-treatmentprocess. The deposition-treatment cycle may be performed 2, 3, or moretimes to deposit multiple cobalt capping layers. Each of the cobaltcapping layers may be deposited to a thickness within a range from about3 Å to about 5 Å during each of the deposition-treatment cycles.

In another example, the copper oxide surface may be exposed to theammonia plasma or the hydrogen plasma for a time period within a rangefrom about 5 seconds to about 15 seconds during a pre-treatment process.The plasma may be exposed to the cobalt capping layer during thepost-treatment process contains nitrogen, ammonia, an ammonia/nitrogenmixture, or hydrogen.

In another embodiment, a method for capping a copper surface on asubstrate is provided which includes positioning a substrate within aprocessing chamber, wherein the substrate contains a copper oxidesurface and a dielectric surface, exposing the copper oxide surface toan ammonia plasma or a hydrogen plasma while forming a metallic coppersurface during a pre-treatment process, exposing the substrate to acobalt precursor gas and hydrogen gas to selectively form a cobaltcapping layer over the metallic copper surface while leaving exposed thedielectric surface during a vapor deposition process, and exposing thecobalt capping layer to a plasma and a reagent selected from the groupconsisting of nitrogen, ammonia, hydrogen, an ammonia/nitrogen mixture,and combinations thereof during a post-treatment process.

In another embodiment, a method for capping a copper surface on asubstrate is provided which includes positioning a substrate within aprocessing chamber, wherein the substrate contains a contaminated coppersurface and a dielectric surface, exposing the contaminated coppersurface to a reducing agent while forming a metallic copper surfaceduring a pre-treatment process, and depositing a cobalt capping materialover the metallic copper surface while leaving exposed the dielectricsurface during a deposition-treatment cycle. In one example, thedeposition-treatment cycle includes exposing the substrate to a cobaltprecursor gas to selectively form a first cobalt layer over the metalliccopper surface while leaving exposed the dielectric surface during avapor deposition process, exposing the first cobalt layer to a plasmacontaining nitrogen, ammonia, an ammonia/nitrogen mixture, or hydrogenduring a treatment process, exposing the substrate to the cobaltprecursor gas to selectively form a second cobalt layer over the firstcobalt layer while leaving exposed the dielectric surface during thevapor deposition process, and exposing the second cobalt layer to theplasma during the treatment process. The method further providesdepositing a dielectric barrier layer over the cobalt capping materialand the dielectric surface.

In some examples, the method provides exposing the substrate to thecobalt precursor gas to selectively form a third cobalt layer over thesecond cobalt layer while leaving exposed the dielectric surface duringthe vapor deposition process, and exposing the third cobalt layer to theplasma during the treatment process.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the inventioncan be understood in detail, a more particular description of theinvention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 depicts a flow chart illustrating a treatment and depositionprocess according to an embodiment described herein;

FIGS. 2A-2E depict schematic views of a substrate at different processsteps according to an embodiment described herein; and

FIG. 3 depicts a flow chart illustrating a deposition process accordingto another embodiment described herein.

DETAILED DESCRIPTION

Embodiments of the invention provide a method that utilizes a cobaltcapping layer or material to prevent copper diffusion and dewetting ininterconnect boundary regions. The transition metal, for example,cobalt, improves copper boundary region properties to promote adhesion,decrease diffusion and agglomeration, and encourage uniform roughnessand wetting of the substrate surface during processing. Embodimentsprovide that a cobalt capping layer may be selectively deposited on acopper contact or surface on a substrate while leaving exposeddielectric surfaces on the substrate.

FIG. 1 depicts a flow chart illustrating process 100 according to anembodiment of the invention. Process 100 may be used to clean and cap acopper contact surface on a substrate post a polishing process. In oneembodiment, steps 110-140 of process 100 may be used on substrate 200,depicted in FIGS. 2A-2E. Process 100 includes exposing a substrate topre-treatment process (step 110), depositing a cobalt capping layer onexposed copper surfaces of the substrate (step 120), exposing thesubstrate to post-treatment process (step 130), and depositing adielectric barrier layer on the substrate (step 140).

FIG. 2A depicts substrate 200 containing dielectric layer 204 disposedover underlayer 202 after being exposed to a polishing process. Coppercontacts 208 are disposed within dielectric layer 204 and are separatedfrom dielectric layer 204 by barrier layer 206. Dielectric layer 204contains a dielectric material, such as a low-k dielectric material. Inone example, dielectric layer 204 contains a low-k dielectric material,such as a silicon carbide oxide material or a carbon doped silicon oxidematerial, for example, BLACK DIAMOND® II low-k dielectric material,available from Applied Materials, Inc., located in Santa Clara, Calif.

Barrier layer 206 may be conformally deposited into the aperture withindielectric layer 204. Barrier layer 206 may be formed or deposited by aPVD process, an ALD, or a CVD process, and may have a thickness within arange from about 5 Å to about 50 Å, preferably, from about 10 Å to about30 Å. Barrier layer 206 may contain titanium, titanium nitride,tantalum, tantalum nitride, tungsten, tungsten nitride, suicidesthereof, derivatives thereof, or combinations thereof. In someembodiments, barrier layer 206 may contain a tantalum/tantalum nitridebilayer or titanium/titanium nitride bilayer. In one example, barrierlayer 206 contains tantalum nitride and metallic tantalum layersdeposited by PVD processes.

During the polishing process, such as a chemical mechanical polishing(CMP) process, the upper surface of copper contacts 208 are exposedacross substrate field 210 and contaminants 212 are formed on coppercontacts 212. Contaminants 212 usually contain copper oxides formedduring or after the polishing process. The exposed surfaces of coppercontacts 208 may be oxidized by peroxides, water, or other reagents inthe polishing solution or by oxygen within the ambient air. Contaminants212 may also include moisture, polishing solution remnants includingsurfactants and other additives, or particles of polished awaymaterials.

At step 110 of process 100, contaminants 212 may be removed fromsubstrate field 210 by exposing substrate 200 to a pre-treatmentprocess. Copper surfaces 214 are exposed once contaminants 212 aretreated or removed from copper contacts 208, as illustrated in FIG. 2B.Copper oxides may be chemically reduced by exposing substrate 200 to areducing agent. The pre-treatment process exposes substrate 200 to thereducing agent during a thermal process or a plasma process. Thereducing agent may have a liquid state, a gas state, a plasma state, orcombinations thereof. Reducing agent that are useful during thepre-treatment process include hydrogen (e.g., H₂ or atomic-H), ammonia(NH₃), a hydrogen and ammonia mixture (H₂/NH₃), atomic-N, hydrazine(N₂H₄), alcohols (e.g., methanol, ethanol, or propanol), derivativesthereof, plasmas thereof, or combinations thereof. Substrate 200 may beexposed to a plasma formed in situ or remotely during the pre-treatmentprocess.

In one embodiment, substrate 200 is exposed to a thermal pre-treatmentprocess to remove contaminants 212 from copper contacts 208 whileforming copper surfaces 214. Substrate 200 may be positioned within aprocessing chamber, exposed to a reducing agent, and heated to atemperature within a range from about 200° C. to about 800° C.,preferably, from about 250° C. to about 600° C., and more preferably,from about 300° C. to about 500° C. Substrate 200 may be heated for atime period within a range from about 2 minutes to about 20 minutes,preferably, from about 5 minutes to about 15 minutes. For example,substrate 200 may be heated to about 500° C. in a processing chambercontaining a hydrogen atmosphere for about 12 minutes.

In another embodiment, substrate 200 is exposed to a plasmapre-treatment process to remove contaminants 212 from copper contacts208 while forming copper surfaces 214. Substrate 200 may be positionedwithin a processing chamber, exposed to a reducing agent, and heated toa temperature within a range from about 100° C. to about 400° C.,preferably, from about 125° C. to about 350° C., and more preferably,from about 150° C. to about 300° C., such as about 200° C. or about 250°C. The processing chamber may produce an in situ plasma or be equippedwith a remote plasma source (RPS). In one embodiment, substrate 200 maybe exposed to the plasma (e.g., in situ or remotely) for a time periodwithin a range from about 2 seconds to about 60 seconds, preferably,from about 3 seconds to about 30 seconds, preferably, from about 5seconds to about 15 seconds, such as about 10 seconds. The plasma may beproduced at a power within the range from about 200 watts to about 1,000watts, preferably, from about 400 watts to about 800 watts. In oneexample, substrate 200 may be exposed to hydrogen gas while a plasma isgenerated at 400 watts for about 10 seconds at about 5 Torr. In anotherexample, substrate 200 may be exposed to ammonia gas while a plasma isgenerated at 800 watts for about 20 seconds at about 5 Torr. In anotherexample, substrate 200 may be exposed to a hydrogen and ammonia gaseousmixture while a plasma is generated at 400 watts for about 15 seconds atabout 5 Torr.

At step 120 of process 100, cobalt capping layer 216 may be selectivelydeposited or formed on copper surfaces 214 while leaving bare theexposed surfaces of dielectric layer 204 across substrate field 210, asillustrated in FIG. 2C. Therefore, along substrate field 210, cobaltcapping layer 216 is selectively deposited on copper surfaces 214 whileleaving the surfaces of dielectric layer 204 free or at leastsubstantially free of cobalt capping layer 216. Initially, cobaltcapping layer 216 may be a continuous layer or a discontinuous layeracross copper surfaces 214, but is a continuous layer after multipledeposition cycles.

Contaminants 218 may collect throughout substrate field 210, such as oncobalt capping layer 216 as well as the surfaces of dielectric layer204, as depicted in FIG. 2C. Contaminants 218 may include by-productsfrom the deposition process, such as carbon, organic residue, precursorresidue, and other undesirable materials collected on substrate field210.

Substrate 200 may be exposed to a plasma formed in situ or remotelyduring the post-treatment process at step 130 of process 100. Thepost-treatment process removes or reduces the amount of contaminantsfrom substrate 200 while further densifying cobalt capping layer 216.The post-treatment process may expose substrate 200 and cobalt cappinglayer 216 to a reducing agent during the plasma process. Reducing agentthat are useful during the post-treatment process include hydrogen(e.g., H₂ or atomic-H), ammonia (NH₃), a hydrogen and ammonia mixture(H₂/NH₃), nitrogen (e.g., N₂ or atomic-N), hydrazine (N₂H₄), derivativesthereof, plasmas thereof, or combinations thereof. Cobalt capping layer216 may be exposed to the plasma during the post-treatment process for atime period within a range from about 2 seconds to about 60 seconds,preferably, from about 3 seconds to about 30 seconds, and morepreferably, from about 5 seconds to about 15 seconds.

In one example, the cobalt capping layer is exposed to a hydrogenplasma, formed by igniting hydrogen gas in situ or remotely of theprocessing chamber. In another example, the cobalt capping layer isexposed to an ammonia plasma, formed by igniting ammonia gas in situ orremotely of the processing chamber. In another example, the cobaltcapping layer is exposed to a hydrogen/ammonia plasma, formed byigniting a mixture of hydrogen gas and ammonia gas in situ or remotelyof the processing chamber.

A plasma may be generated external from the processing chamber, such asby a remote plasma source (RPS) system, or preferably, the plasma may begenerated in situ a plasma capable deposition chamber, such as a PE-CVDchamber during a plasma treatment process, such as in steps 130 or 330.The plasma may be generated from a microwave (MW) frequency generator ora radio frequency (RF) generator. In a preferred example, an in situplasma is generated by a RF generator. The processing chamber may bepressurized during the plasma treatment process at a pressure within arange from about 0.1 Torr to about 80 Torr, preferably from about 0.5Torr to about 10 Torr, and more preferably, from about 1 Torr to about 5Torr. Also, the chamber or the substrate may be heated to a temperatureof less than about 500° C., preferably within a range from about 100° C.to about 450° C., and more preferably, from about 150° C. to about 400°C., for example, about 300° C.

During treatment processes, a plasma may be ignited within theprocessing chamber for an in situ plasma process, or alternative, may beformed by an external source, such as a RPS system. The RF generator maybe set at a frequency within a range from about 100 kHz to about 60 MHz.In one example, a RF generator, with a frequency of 13.56 MHz, may beset to have a power output within a range from about 100 watts to about1,000 watts, preferably, from about 250 watts to about 600 watts, andmore preferably, from about 300 watts to about 500 watts. In oneexample, a RF generator, with a frequency of 350 kHz, may be set to havea power output within a range from about 200 watts to about 2,000 watts,preferably, from about 500 watts to about 1,500 watts, and morepreferably, from about 800 watts to about 1,200 watts, for example,about 1,000 watts. A surface of substrate may be exposed to a plasmahaving a power per surface area value within a range from about 0.01watts/cm² to about 10.0 watts/cm², preferably, from about 0.05 watts/cm²to about 6.0 watts/cm².

In another embodiment, step 120 is repeated at least once, two times, ormore. Step 120 may be performed one time to form a single layer ofcobalt capping layer 216, or performed multiple times to form multiplelayers of cobalt capping layer 216, such as 2, 3, 4, 5, or more layersof cobalt capping layer 216. In another embodiment, steps 120 and 130are sequentially repeated at least once, if not, 2, 3, 4 or more times.Cobalt capping layer 216 may be deposited having a thickness within arange from about 2 Å to about 30 Å, preferably, from about 3 Å to about25 Å, more preferably, from about 4 Å to about 20 Å, and morepreferably, from about 5 Å to about 10 Å, such as about 7 Å or about 8Å. In one example, two cycles of steps 120 and 130 and performed to formcobalt capping layer 216 with a thickness of about 7 Å. In anotherexample, three cycles of steps 120 and 130 and performed to form cobaltcapping layer 216 with a thickness of about 8 Å.

Cobalt capping layer 216 may be deposited by thermal decomposition of acobalt containing precursor carried by an inert gas during step 120. Areducing gas may be co-flowed or alternately pulsed into the processingchamber along with the cobalt precursor. The substrate may be heated toa temperature within a range from about 50° C. to about 600° C.,preferably, from about 100° C. to about 500° C., and more preferably,from about 200° C. to about 400° C. Alternatively, cobalt capping layer216 may be deposited by exposing the substrate to a cobalt containingprecursor gas in an ALD or CVD process.

FIG. 3 depicts a flow-chart of process 300 which may be used to formcobalt-containing materials, such as cobalt capping layer 216. In oneembodiment, process 300 includes exposing a substrate to a depositiongas to form a cobalt capping material (step 310), optionally purging thedeposition chamber (step 320), exposing the substrate to a plasmatreatment process (step 330), purging the deposition chamber (step 340),and determining if a predetermined thickness of the cobalt cappingmaterial has been formed on the substrate (step 350). In one embodiment,the cycle of steps 310-350 may be repeated if the cobalt cappingmaterial has not been formed having the predetermined thickness. Inanother embodiment, the cycle of steps 310 and 330 may be repeated ifthe cobalt capping material has not been formed having the predeterminedthickness. Alternately, process 300 may be stopped once the cobaltcapping material has been formed having the predetermined thickness.

In one embodiment, a method for capping a copper surface on a substrateis provided which includes exposing the substrate to a cobalt precursorgas and hydrogen gas to selectively form a cobalt capping layer over themetallic copper surface while leaving exposed the dielectric surfaceduring a vapor deposition process, and exposing the cobalt capping layerto a plasma and a reagent, such as nitrogen, ammonia, hydrogen, anammonia/nitrogen mixture, or combinations thereof during apost-treatment process.

In another embodiment, a method for capping a copper surface on asubstrate is provided which includes depositing a cobalt cappingmaterial over the metallic copper surface while leaving exposed thedielectric surface during a deposition-treatment cycle. In one example,the deposition-treatment cycle includes exposing the substrate to acobalt precursor gas to selectively form a first cobalt layer over themetallic copper surface while leaving exposed the dielectric surfaceduring a vapor deposition process, exposing the first cobalt layer to aplasma containing nitrogen, ammonia, an ammonia/nitrogen mixture, orhydrogen during a treatment process. The method further providesexposing the substrate to the cobalt precursor gas to selectively form asecond cobalt layer over the first cobalt layer while leaving exposedthe dielectric surface during the vapor deposition process, and exposingthe second cobalt layer to the plasma during the treatment process.

In some examples, the method provides exposing the substrate to thecobalt precursor gas to selectively form a third cobalt layer over thesecond cobalt layer while leaving exposed the dielectric surface duringthe vapor deposition process, and exposing the third cobalt layer to theplasma during the treatment process.

Suitable cobalt precursors for forming cobalt-containing materials(e.g., metallic cobalt or cobalt alloys) by CVD or ALD processesdescribed herein include cobalt carbonyl complexes, cobalt amidinatescompounds, cobaltocene compounds, cobalt dienyl complexes, cobaltnitrosyl complexes, derivatives thereof, complexes thereof, plasmathereof, or combinations thereof. In some embodiments, cobalt materialsmay be deposited by CVD and ALD processes further described in commonlyassigned U.S. Pat. No. 7,264,846 and U.S. Ser. No. 10/443,648, filed May22, 2003, and published as US 2005-0220998, which are hereinincorporated by reference.

In some embodiments, cobalt carbonyl compounds or complexes may beutilized as cobalt precursors. Cobalt carbonyl compounds or complexeshave the general chemical formula (CO)_(x)Co_(y)L_(z), where X may be 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, Y may be 1, 2, 3, 4, or 5, and Zmay be 1, 2, 3, 4, 5, 6, 7, or 8. The group L is absent, one ligand ormultiple ligands, that may be the same ligand or different ligands, andinclude cyclopentadienyl, alkylcyclopentadienyl (e.g.,methylcyclopentadienyl or pentamethylcyclopentadienyl), pentadienyl,alkylpentadienyl, cyclobutadienyl, butadienyl, ethylene, allyl (orpropylene), alkenes, dialkenes, alkynes, acetylene, bytylacetylene,nitrosyl, ammonia, derivatives thereof, complexes thereof, plasmathereof, or combinations thereof. Some exemplary cobalt carbonylcomplexes include cyclopentadienyl cobalt bis(carbonyl) (CpCo(CO)₂),tricarbonyl allyl cobalt ((CO)₃Co(CH₂CH═CH₂)), dicobalt hexacarbonylbytylacetylene (CCTBA, (CO)₆Co₂(HC≡C^(t)Bu)), dicobalt hexacarbonylmethylbytylacetylene ((CO)₆Co₂(MeC≡C^(t)Bu)), dicobalt hexacarbonylphenylacetylene ((CO)₆Co₂(HC≡CPh)), hexacarbonyl methylphenylacetylene((CO)₆Co₂(MeC≡CPh)), dicobalt hexacarbonyl methylacetylene((CO)₆Co₂(HC≡CMe)), dicobalt hexacarbonyl dimethylacetylene((CO)₆Co₂(MeC≡CMe)), derivatives thereof, complexes thereof, plasmathereof, or combinations thereof.

In another embodiment, cobalt amidinates or cobalt amido complexes maybe utilized as cobalt precursors. Cobalt amido complexes have thegeneral chemical formula (RR′N)_(x)Co, where X may be 1, 2, or 3, and Rand R′ are independently hydrogen, methyl, ethyl, propyl, butyl, alkyl,silyl, alkylsilyl, derivatives thereof, or combinations thereof. Someexemplary cobalt amido complexes includebis(di(butyldimethylsilyl)amido) cobalt (((BuMe₂Si)₂N)₂Co),bis(di(ethyidimethylsilyl)amido) cobalt (((EtMe₂Si)₂N)₂Co),bis(di(propyidimethylsilyl)amido) cobalt (((PrMe₂Si)₂N)₂Co),bis(di(trimethylsilyl)amido) cobalt (((Me₃Si)₂N)₂Co),tris(di(trimethylsilyl)amido) cobalt (((Me₃Si)₂N)₃Co), derivativesthereof, complexes thereof, plasma thereof, or combinations thereof.

Some exemplary cobalt precursors include methylcyclopentadienyl cobaltbis(carbonyl) (MeCpCo(CO)₂), ethylcyclopentadienyl cobalt bis(carbonyl)(EtCpCo(CO)₂), pentamethylcyclopentadienyl cobalt bis(carbonyl)(Me₅CpCo(CO)₂), dicobalt octa(carbonyl) (Co₂(CO)₈), nitrosyl cobalttris(carbonyl) ((ON)Co(CO)₃), bis(cyclopentadienyl) cobalt,(cyclopentadienyl) cobalt (cyclohexadienyl), cyclopentadienyl cobalt(1,3-hexadienyl), (cyclobutadienyl) cobalt (cyclopentadienyl),bis(methylcyclopentadienyl) cobalt, (cyclopentadienyl) cobalt(5-methylcyclopentadienyl), bis(ethylene) cobalt(pentamethylcyclopentadienyl), cobalt tetracarbonyl iodide, cobalttetracarbonyl trichlorosilane, carbonyl chloridetris(trimethylphosphine) cobalt, cobalttricarbonyl-hydrotributylphosphine, acetylene dicobalt hexacarbonyl,acetylene dicobalt pentacarbonyl triethylphosphine, derivatives thereof,complexes thereof, plasma thereof, or combinations thereof.

Suitable reagents, including reducing agents, that are useful to formcobalt-containing materials (e.g., metallic cobalt, cobalt cappinglayers, or cobalt alloys) by processes described herein include hydrogen(e.g., H₂ or atomic-H), atomic-N, ammonia (NH₃), hydrazine (N₂H₄), ahydrogen and ammonia mixture (H₂/NH₃), borane (BH₃), diborane (B₂H₆),triethylborane (Et₃B), silane (SiH₄), disilane (Si₂H₆), trisilane(Si₃H₈), tetrasilane (Si₄H₁₀), methyl silane (SiCH₆), dimethylsilane(SiC₂H₈), phosphine (PH₃), derivatives thereof, plasmas thereof, orcombinations thereof.

During step 140 of process 100, dielectric barrier layer 220 may bedeposited over cobalt capping layer 216 and on substrate 200, asdepicted in FIG. 2E. Dielectric barrier layer 220 having a lowdielectric constant may be deposited on substrate 200, across substratefield 210, and over cobalt capping layer 216. Dielectric barrier layer220 may contain a low-k dielectric material, such as silicon carbide,silicon nitride, silicon oxide, silicon oxynitride, silicon carbideoxide or carbon doped silicon oxide material, derivatives thereof, orcombinations thereof. In one example, BLOK® low-k dielectric material,available from Applied Materials, Inc., located in Santa Clara, Calif.,may be utilized as a low-k dielectric material for dielectric barrierlayer 220. An example of a suitable material for dielectric barrierlayer 220 is a silicon carbide based film formed using CVD or plasmaenhanced CVD (PE-CVD) processes such as the processes described incommonly assigned U.S. Pat. Nos. 6,537,733, 6,790,788, and 6,890,850,which are herein incorporated by reference.

An ALD processing chamber used during embodiments described herein isavailable from Applied Materials, Inc., located in Santa Clara, Calif. Adetailed description of an ALD processing chamber may be found incommonly assigned U.S. Pat. Nos. 6,916,398 and 6,878,206, commonlyassigned U.S. Ser. No. 10/281,079, filed on Oct. 25, 2002, and publishedas U.S. Pub. No. 2003-0121608, and commonly assigned U.S. Ser. Nos.11/556,745, 11/556,752, 11/556,756, 11/556,758, 11/556,763, each filedNov. 6, 2006, and published as U.S. Pub. Nos. 2007-0119379,2007-0119371, 2007-0128862, 2007-0128863, and 2007-0128864, which arehereby incorporated by reference in their entirety. In anotherembodiment, a chamber configured to operate in both an ALD mode as wellas a conventional CVD mode may be used to deposit cobalt-containingmaterials is described in commonly assigned U.S. Pat. No. 7,204,886,which is incorporated herein by reference in its entirety. A detaileddescription of an ALD process for forming cobalt-containing materials isfurther disclosed in commonly assigned U.S. Ser. No. 10/443,648, filedon May 22, 2003, and published as U.S. Pub. No. 2005-0220998, andcommonly assigned U.S. Pat. No. 7,264,846, which are hereby incorporatedby reference in their entirety. In other embodiments, a chamberconfigured to operate in both an ALD mode as well as a conventional CVDmode that may be used to deposit cobalt-containing materials is the TXZ®showerhead and CVD chamber available from Applied Materials, Inc.,located in Santa Clara, Calif.

“Substrate surface” or “substrate,” as used herein, refers to anysubstrate or material surface formed on a substrate upon which filmprocessing is performed during a fabrication process. For example, asubstrate surface on which processing may be performed include materialssuch as monocrystalline, polycrystalline or amorphous silicon, strainedsilicon, silicon on insulator (SOI), doped silicon, silicon germanium,germanium, gallium arsenide, glass, sapphire, silicon oxide, siliconnitride, silicon oxynitride, and/or carbon doped silicon oxides, such asSiO_(x)C_(y), for example, BLACK DIAMOND® low-k dielectric, availablefrom Applied Materials, Inc., located in Santa Clara, Calif. Substratesmay have various dimensions, such as 200 mm or 300 mm diameter wafers,as well as, rectangular or square panes. Unless otherwise noted,embodiments and examples described herein are preferably conducted onsubstrates with a 200 mm diameter or a 300 mm diameter, more preferably,a 300 mm diameter. Embodiments of the processes described herein depositcobalt silicide materials, metallic cobalt materials, and othercobalt-containing materials on many substrates and surfaces, especially,silicon-containing dielectric materials. Substrates on which embodimentsof the invention may be useful include, but are not limited tosemiconductor wafers, such as crystalline silicon (e.g., Si<100> orSi<111>), silicon oxide, strained silicon, silicon germanium, doped orundoped polysilicon, doped or undoped silicon wafers, and patterned ornon-patterned wafers. Substrates may be exposed to a pre-treatmentprocess to polish, etch, reduce, oxidize, hydroxylate, anneal, and/orbake the substrate surface.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for capping a copper surface on a substrate, comprising:positioning a substrate within a processing chamber, wherein thesubstrate comprises a contaminated copper surface and a dielectricsurface; exposing the contaminated copper surface to a reducing agentwhile forming a metallic copper surface during a pre-treatment process;exposing the substrate to a cobalt precursor gas to selectively form acobalt capping layer over the metallic copper surface while leavingexposed the dielectric surface during a vapor deposition process; anddepositing a dielectric barrier layer over the cobalt capping layer andthe dielectric surface.
 2. The method of claim 1, further comprisingchemically reducing copper oxides on the contaminated copper surface toform the metallic copper surface during the pre-treatment process. 3.The method of claim 1, wherein the contaminated copper surface isexposed to the reducing agent and a plasma is ignited during thepre-treatment process, the reducing agent comprises a reagent selectedfrom the group consisting of nitrogen (N₂), ammonia (NH₃), hydrogen(H₂), ammonia/nitrogen mixture, and combinations thereof.
 4. The methodof claim 3, wherein the contaminated copper surface is exposed to theplasma for a time period within a range from about 5 seconds to about 15seconds.
 5. The method of claim 1, wherein the reducing agent compriseshydrogen gas, the pre-treatment process is a thermal process, and thesubstrate is heated to a temperature within a range from about 200° C.to about 400° C. during the thermal process.
 6. The method of claim 1,further comprising exposing the cobalt capping layer to a reagent and aplasma during a post-treatment process prior to depositing thedielectric barrier layer, the reagent is selected from the groupconsisting of nitrogen (N₂), ammonia (NH₃), hydrogen (H₂),ammonia/nitrogen mixture, and combinations thereof.
 7. The method ofclaim 6, wherein a deposition-treatment cycle comprises performing thevapor deposition process and subsequently the post-treatment process,and the deposition-treatment cycle is performed 2, 3, or more times todeposit multiple cobalt capping layers.
 8. The method of claim 7,wherein each of the cobalt capping layers is deposited to a thicknesswithin a range from about 3 Å to about 5 Å during each of thedeposition-treatment cycles.
 9. The method of claim 1, wherein thecobalt capping layer has a thickness within a range from about 4 Å toabout 20 Å.
 10. The method of claim 1, wherein the cobalt capping layerhas a thickness of less than about 10 Å.
 11. The method of claim 10,wherein the substrate is exposed to a deposition gas comprising thecobalt precursor gas and hydrogen gas during the vapor depositionprocess, the vapor deposition process is a thermal chemical vapordeposition process or an atomic layer deposition process.
 12. The methodof claim 1, wherein the cobalt precursor gas comprises a cobaltprecursor which has the general chemical formula (CO)_(x)Co_(y)L_(z),wherein: X is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12; Y is 1, 2, 3, 4,or 5; Z is 1, 2, 3, 4, 5, 6, 7, or 8; and L is a ligand independentlyselected from the group consisting of cyclopentadienyl,alkylcyclopentadienyl, methylcyclopentadienyl,pentamethylcyclopentadienyl, pentadienyl, alkylpentadienyl,cyclobutadienyl, butadienyl, allyl, ethylene, propylene, alkenes,dialkenes, alkynes, nitrosyl, ammonia, derivatives thereof, andcombinations thereof.
 13. The method of claim 1, wherein the cobaltprecursor gas comprises a cobalt precursor selected from the groupconsisting of tricarbonyl allyl cobalt, cyclopentadienyl cobaltbis(carbonyl), methylcyclopentadienyl cobalt bis(carbonyl),ethylcyclopentadienyl cobalt bis(carbonyl), pentamethylcyclopentadienylcobalt bis(carbonyl), dicobalt octa(carbonyl), nitrosyl cobalttris(carbonyl), bis(cyclopentadienyl) cobalt, (cyclopentadienyl) cobalt(cyclohexadienyl), cyclopentadienyl cobalt (1,3-hexadienyl),(cyclobutadienyl) cobalt (cyclopentadienyl), bis(methylcyclopentadienyl)cobalt, (cyclopentadienyl) cobalt (5-methylcyclopentadienyl),bis(ethylene) cobalt (pentamethylcyclopentadienyl), derivatives thereof,complexes thereof, plasmas thereof, and combinations thereof.
 14. Themethod of claim 13, wherein the cobalt precursor comprisescyclopentadienyl cobalt bis(carbonyl).
 15. A method for capping a coppersurface on a substrate, comprising: positioning a substrate within aprocessing chamber, wherein the substrate comprises a copper oxidesurface and a dielectric surface; exposing the copper oxide surface toan ammonia plasma or a hydrogen plasma while forming a metallic coppersurface during a pre-treatment process; exposing the substrate to acobalt precursor gas to selectively form a cobalt capping layer over themetallic copper surface while leaving exposed the dielectric surfaceduring a vapor deposition process; exposing the cobalt capping layer toa plasma during a post-treatment process; and depositing a dielectricbarrier layer over the cobalt capping layer and the dielectric surface.16. The method of claim 15, wherein a deposition-treatment cyclecomprises performing the vapor deposition process and subsequently thepost-treatment process, and the deposition-treatment cycle is performed2, 3, or more times to deposit multiple cobalt capping layers.
 17. Themethod of claim 16, wherein each of the cobalt capping layers isdeposited to a thickness within a range from about 3 Å to about 5 Åduring each of the deposition-treatment cycles.
 18. The method of claim15, wherein the copper oxide surface is exposed to the ammonia plasma orthe hydrogen plasma for a time period within a range from about 5seconds to about 15 seconds during a pre-treatment process.
 19. Themethod of claim 15, wherein a reagent and the plasma are exposed to thecobalt capping layer during the post-treatment process, and the reagentis selected from the group consisting of nitrogen (N₂), ammonia (NH₃),hydrogen (H₂), ammonia/nitrogen mixture, and combinations thereof.
 20. Amethod for capping a copper surface on a substrate, comprising:positioning a substrate within a processing chamber, wherein thesubstrate comprises a copper oxide surface and a dielectric surface;exposing the copper oxide surface to an ammonia plasma or a hydrogenplasma while forming a metallic copper surface during a pre-treatmentprocess; exposing the substrate to a cobalt precursor gas and hydrogengas to selectively form a cobalt capping layer over the metallic coppersurface while leaving exposed the dielectric surface during a vapordeposition process; and exposing the cobalt capping layer to a plasmaand a reagent selected from the group consisting of nitrogen (N₂),ammonia (NH₃), hydrogen (H₂), ammonia/nitrogen mixture, and combinationsthereof during a post-treatment process.
 21. The method of claim 20,wherein a deposition-treatment cycle comprises performing the vapordeposition process and subsequently the post-treatment process, and thedeposition-treatment cycle is performed 2, 3, or more times to depositmultiple cobalt capping layers.
 22. The method of claim 21, wherein eachof the cobalt capping layers is deposited to a thickness within a rangefrom about 3 Å to about 5 Å during each of the deposition-treatmentcycles.
 23. The method of claim 20, further comprising depositing adielectric barrier layer over the cobalt capping layer and thedielectric surface.
 24. A method for capping a copper surface on asubstrate, comprising: positioning a substrate within a processingchamber, wherein the substrate comprises a contaminated copper surfaceand a dielectric surface; exposing the contaminated copper surface to areducing agent while forming a metallic copper surface during apre-treatment process; depositing a cobalt capping material over themetallic copper surface while leaving exposed the dielectric surfaceduring a deposition-treatment cycle, comprising: exposing the substrateto a cobalt precursor gas to selectively form a first cobalt layer overthe metallic copper surface while leaving exposed the dielectric surfaceduring a vapor deposition process; exposing the first cobalt layer to aplasma comprising nitrogen, ammonia, an ammonia/nitrogen mixture, orhydrogen during a treatment process; exposing the substrate to thecobalt precursor gas to selectively form a second cobalt layer over thefirst cobalt layer while leaving exposed the dielectric surface duringthe vapor deposition process; exposing the second cobalt layer to theplasma during the treatment process; and depositing a dielectric barrierlayer over the cobalt capping material and the dielectric surface. 25.The method of claim 24, further comprising: exposing the substrate tothe cobalt precursor gas to selectively form a third cobalt layer overthe second cobalt layer while leaving exposed the dielectric surfaceduring the vapor deposition process; and exposing the third cobalt layerto the plasma during the treatment process.